The use of the in-field critical current density, J(c)(0.1 T), as a betterdescriptor of (Bi, Pb)(2)Sr2Ca2Cu3Ox/Ag tape performance

Extended voltage-current characteristics of 13 optimized (Bi, Pb)(2)Sr2Ca2C u3Ox/Ag multifilamentary tapes from four different manufacturers were exten sively evaluated so as to extract the field-dependent J(c)(H), the characte ristic field H-p obtained from the relation J(c)similar to exp(-H/H-p), and the irreversibility field H*. Values of the self-field critical current de nsity J(c)(0 T, 77 K) ranged from 12 to 63 kA/cm(2), I-c(0 T,77 K) from 11 to 139 A, H-p from 128 to 204 mT, and H* from 163 to 369 mT, this range thu s being representative of present optimized composites. Self-field can stro ngly dominate J(c)(H) in fields below 20 mT; thus, J(c)(0 T,77 K) is a flaw ed parameter for characterizing tapes because of its very heavy dependence on self-field. We propose that a much better descriptor of tape performance is J(c)(0.1 T,77 K), because it lies outside the self-field and weak-link- destruction regimes and clearly within the flux-pinning-controlled domain w here the connectivity-determined active cross-section carrying current is c onstant. (C) 1999 American Institute of Physics. [S0003-6951(99)02546-2].